The present invention relates generally to a machining apparatus and more particularly to a thermal mechanical apparatus for machining composite materials.
“Skiving” is a term used to describe a machining process in which small portions of material are removed from a part. A skive is the apparatus used to remove portions of the part. Laser skives or mechanical skives are currently used on products in industries including semiconductor, aerospace, and photographic and optical equipment.
Laser skives have been used to remove composite layer(s) when the composite utilizes an organic fiber (i.e., a fiber containing carbon, hydrogen, nitrogen, and/or oxygen compounds) such as graphite or an organic polymer matrix such as epoxy. Laser skiving relies on the thermal decomposition of the organic constituents of the composite in the presence of oxygen (oxidation) or the exclusion of oxygen (pyrolysis). However, laser skiving becomes ineffective for material removal when the composite being machined utilizes an inorganic fiber or filler such as fiberglass, metal or silica, or has organic constituents which thermally convert to inorganic constituents (e.g., silicone). Additionally, laser skives are not easily controllable to remove composite layers having non-uniform thickness or surface irregularities.
Mechanical skiving also has drawbacks which include the fact that it may be difficult to dimensionally control the machined cavity produced. For example, when the surface of the composite layer being exposed by machining is thin and/or is located in a position difficult to reference by traditional machining techniques, the ability to machine to the surface of the layer can result in damage to the layer or failure to adequately expose the layer. Inaccurate machining can impair desired properties of the composite such as the ability of the constituents of the composite to transfer and/or convert electrical energy into heat energy.